the worst you can do is reply to them. Once you reply, even if you say "bugger off", they'll keep emailing you, give your email addy to their cohorts, etc.
there's really not a whole lot you can do, unless youre willing to bait them.
if you report the offense (fraud/spam) to yahoo, it wont make any difference because these scammers have tons of email accounts.
how they typically do their email -
one or more accounts for personal use
one or more accounts for communicating with cohorts
multiple accounts for sending spam
multiple accounts for communication with victims
if you look, it has where your reply is to go to a different email addy than the one that sent the spam. the reply to addy is where the real fraud takes place and where they're communicating with victims. the spam account only sends out the spam, thus it's disposable and your reporting and getting it shut down wont do anything to slow them down.
BTW, the fact that they used James Lxxxx is simply a coincidence. They take a common first name, and add your last name, then send the spam.
I know you said that your name isnt out there with your email acct, but it's somewhere since one of them found ya. They get their lists from lots of places - forums, yahoo member lists, aol lists, website guestbooks, etc. I had one that sent me a 419 email to an email account of mine and it's not out there anywhere that i know of. the ONLY way i can think of that they could have gotten my email addy was by using an email addy generator like the spammers use. acct is email@example.com
If you have time to kill (and I mean TONS of time to kill) can always bait him
if you do bait him, do it safely! always use an anonymous email account that hides your IP addy (fastmail or gmail), never ever give out any of your real info (not even your real name), etc. For safe baiting help, join http://www.419eater.com
if you sign up to the eater, dont put any real info in profile and dont use name in username. reason why is cause the scammers are known to stop by and read the eater from time to time.
if you need a gmail invite to set up an anonymous account with fake info, let me know
oh, as to why so much concern about being fully anon when baiting, although these lads (scammers) are in nigeria, south africa, etc, they often have cohorts in other countries such as the UK and the US. There's a whole mob of them in Houston, for example.